To prepare for chimney swifts, act quickly
Just a few days ago, a friend asked when chimney swifts will return. "They nest in my chimney every year," he explained, "make all kinds of noise, and usually a few get in the house. Is there still time to get a cap on my chimney to keep them out?"
Yes, but not much. I look for chimney swifts to return in mid-April, but precise arrival dates are tied to weather, particularly temperature, which determines the activity of flying insects. They arrived in Austin, Texas, on March 3 and in St. Petersburg, Fla., on March 13. If it warms up, swifts could return here in early April. So if swifts are a concern, get chimneys capped in the next two weeks.
For the uninitiated, chimney swifts are those familiar summer residents that spend all day sweeping the sky for flying insects while twittering incessantly. At a glance, they resemble flying cigars.
At dusk, they assemble and descend en masse into chimneys where they roost for the night. Hundreds or even thousands may roost in abandoned industrial chimneys. Swifts are most common in towns and cities where chimneys are seldom in short supply. They winter in the upper Amazon basin of Peru, Ecuador, Chile, and Brazil.
Hundreds of years ago, chimney swifts nested in tall hollow trees. But as old growth forests disappeared, swifts adapted to other tall, dark, hollow structures such as chimneys, silos, abandoned wells and barns.
Details
Swifts are born to fly. Their long narrow wings, enable rapid, agile flight. They descend into chimneys headfirst, then flip tail-first once inside. There they perch by clinging to the vertical wall. All four toes on each foot are directed forward so they can cling tightly to rough, vertical surfaces. Their tail feathers are tipped with stiff spines that stabilize them while roosting. But because they lack a hind toe, they cannot perch or walk as most birds do.
Nesting begins in early May. Both parents use their strong feet to collecting nesting material in flight. They swoop by small dead twigs, grasp them, snap them off and carry them back to the nest site in their bills. Inside the chimney a layer of sticky saliva is applied to the twig. Then the twig is cemented to the chimney wall and to other twigs. Eventually a nesting platform with a shallow cup forms. A typical swift nest measures about 3 by 4 inches, can take 18 to 30 days to build, and may be placed as much as 30 feet below the opening of the chimney.
The female swift lays a clutch of four eggs over a period of seven to eight days. The parents share incubation duties for about 19 days until the eggs hatch. Young swifts start climbing the wall near the nest about 19 days after hatching, but their first flight comes about 30 days after hatching.
Nesting habits
Thanks to the extended nesting period, swifts in the temperate latitudes nest only once each year. And though you may see dozens or even hundreds of swifts return to a chimney at dusk, they are not colonial nesters. Usually just a few pairs nest in a chimney; the rest are nonbreeders using the structure to roost.
As more and more people cap their chimneys to keep swifts and other wildlife out of their homes swifts will find it increasingly difficult to locate nesting sites. Some might return to hollow trees and caves, but a group in Texas has had great success with artificial chimneys. They're based on a design developed in 1915 by Althea Sherman, whose observations remain the foundation of our understanding of chimney swift nesting biology.
To learn more about chimney swifts, including how to build an artificial chimney, visit www.chimneyswifts.org, the Web site of the North American Chimney Swift Nest Site Research Project (P.O. Box 300369, Austin, TX 78703). An artificial chimney, which must be at least 8 feet tall, is a major project that requires a concrete foundation, but researchers report that most are used by swifts the first nesting season they're available.
Send questions and comments to Dr. Scott Shalaway, R.D. 5, Cameron, W.Va. 26033 or via e-mail to sshalaway@aol.com.